Effect of Rotational Speed Mismatch on a Twin Propeller System: Aeroacoustics Study

A comprehensive aeroacoustics study was conducted on distributed electric propulsion (DEP) systems, focusing on small-scale, novel aircraft within the Urban Air Mobility (UAM) sector. This study investigates the interactions between noise radiation fields generated by each propeller, with a particular emphasis on a twin propeller system. A detailed comparison is made between synchronised and non-synchronised rotational speed configurations across a wide range of propeller rotational speeds, examining both static (or hover) and forward flight regimes. The study reveals that the far-field noise signatures are influenced by the interactions between the noise radiation fields, rather than just the individual propeller contributions. Notably, in both static and forward flight regimes, the non-synchronised configurations at higher rotational speeds demonstrated a greater decrease in noise levels compared to those at lower rotational speeds. Furthermore, this reduction in sound pressure levels was found to be more pronounced in forward flight than in the static flight regime. This study highlights the dynamics of noise interactions in DEP systems and their implications for noise management in future urban air transport systems.